Spatial Genetic Structure in the Mount Vernon Prairie Population of Rudbeckia Hirta

Date of Graduation

Summer 1992


Master of Science in Biology



Committee Chair

John Heywood


It has frequently been predicted that genetic variation in plant populations will be structured in space as a result of isolation by distance, but this prediction has seldom been tested. This study quantified the magnitude and scale of spatial genetic structure in a natural population of the prairie plant, Rudbeckia hirta. A total of 204 randomly distributed pairs of nearest neighbors was sampled from a 6.56 hectare area within Mount Vernon Prairie in Lawrence County, MIssouri. Analysis of spatial structure was based on three polymorphic loci (PGI-1, LAP-1) assayed by cellulose acetate electrophoresis. Significant spatial structure was evident for PGI-1 and LAP-1, but not for AAT-1. At the two loci with significant spatial structure, the scale of structure was extremely small, with genetic correlation approaching zero for interplant distances over a few meters. The small patch size is possibly an indicator of the structure being very recent in origin, thorough the process of isolation by distance. The structure may be partially destroyed by the mowing of the prairie every other year. Variation among loci in the manitude of spatial structute suggests that selection, in addition to isolation by distance, may be influencing the spatial patterning of genetic variation in this population. Mean plant size was not correlated significantly with heterozygosity at either single or multiple loci; there was not a trend toward heterozygotes being larger or smaller in the population.

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© Anthony Lee Hampton